: Have 2 questions

I got 2 questions, if anyone can answer one or both of them, ill appreciate it. thanks!
8. Why is it difficult to measure the perihelion advance of the planet Venus?
9. You are in an elevator at the top of the CN tower. You have a pendulum
and allow it to oscillate. The elevator falls to the ground after someone
cuts its support cables. What does the pendulum do? Ignore the air
resistance acting on the pendulum and the elevator.